Add a property grid to the widget library

[matt-edmondson]

Closes #379.

ImGuiWidgets.PropertyGrid lays out one labelled editor per property in a two-column resizable table. It is immediate mode like the rest of the library: it holds no model, each row edits a variable by reference and returns whether it changed, and Changed accumulates those answers so the whole grid can be tested once.

using (ImGuiWidgets.PropertyGrid grid = new("Settings", options))
{
    using (grid.Section("Basics"))
    {
        grid.Value("Visible", ref visible);            // bool
        grid.Value("Quantity", ref quantity, 0, 100);  // int, clamped
        grid.Value("Name", ref name);                  // string
        grid.Enum("Mode", ref mode);
    }

    grid.Value("Offset", ref offset);   // Vector2/Vector3, float or double
    grid.Value("Tint", ref tint);       // ktsu.Semantics.Color.Color
    grid.FilePath("Config", ref configPath);
    grid.DirectoryPath("Output", ref outputFolder);
    grid.ImagePath("Icon", ref iconPath);   // with a thumbnail beneath it
    grid.List("Tags", tags);
}

What is covered

Everything the issue asked for. One overloaded Value row covers bool, int, long, float, double, string, Vector2/Vector3 and their new DoubleVector2/DoubleVector3 counterparts, and the semantic Color; Enum, the three path rows and List cover the rest. The numeric rows have clamped overloads taking a range.

A List row draws one editor per element, a + to append and an x to remove. Any row method is an element editor, so there is an overload per supported element type, plus FilePathList/DirectoryPathList/ImagePathList for the three whose element type is also a string, and a generic overload taking an editor and a factory for anything else.

A collapsed section holds its own rows back

Section returns a SectionScope disposable, so a section is a using block like every other scope in this library — there is nothing to remember to call, and forgetting an EndSection no longer unbalances ImGui's tree stack.

The scope does more than pair the call: while the section is collapsed it raises the grid's suppression depth and every row draws nothing, so the rows inside are written exactly as they are anywhere else, with no test around them. That is the same answer the grid already gave for a table that never opened, so there is one rule rather than two, and a depth rather than a flag is what lets a section nested inside a collapsed one stay balanced on its own. SectionScope.IsOpen remains for the one case suppression cannot cover: skipping work that costs something to prepare before a row can be called.

Paths and thumbnails are delegated, not owned

ktsu.ImGui.Widgets has no business knowing how the host picks files, and reaching for Hexa's own dialogs would make the deferred-drawing pump a hard requirement of every property grid. So a browse button raises PropertyGridOptions.OnBrowse with a PropertyPathRequest instead. A dialog outlives the frame that opened it, so the request carries no reference to the value: Complete records the answer under the row's ImGui id — safe from any thread and any later frame — and the row adopts it on its next draw. Completing with null leaves the value alone, which is what a cancelled dialog should do. Without a handler the browse button is disabled and paths can still be typed.

Texture upload lives in ktsu.ImGui.App, which this library deliberately does not reference, so an image row asks PropertyGridOptions.ThumbnailResolver for a texture id and draws an empty preview frame when there is none, keeping its height stable once a picture appears.

Other options: ReadOnly, LabelColumnWeight/LabelColumnWidth, ListsStartExpanded, ThumbnailSize, FloatFormat/DoubleFormat.

Demo and tests

• examples/ImGuiWidgetsDemo gains a Property Grid section showing every row type, with read-only and label-width toggles, browsing wired to Hexa's file dialogs and thumbnails wired to ImGuiApp.GetOrLoadTexture.
• tests/ImGui.Widgets.UITests/PropertyGridTests.cs — 23 headless tests covering every row type, change reporting, read-only, the browse round trip (including cancellation and the kind each row asks for), thumbnails with and without a texture, list add/remove/edit, and sections: every row type surviving a collapsed one, nesting, IsOpen, and rows after a section not being held back by it.
• tests/ImGuiWidgetsDemo.UITests drives the new demo section end to end.

The suites caught a real bug: every browse button shared one ImGui id, as did the add buttons of two lists in one grid, because a row draws into a single id stack. Each button's id now carries its row's label.

Verification

• dotnet build ImGui.sln -c Release — clean.
• tests/ImGui.Widgets.UITests — 340/340 pass (23 of them this widget's).
• tests/ImGui.Widgets.Tests — 256/256 pass.
• tests/ImGuiWidgetsDemo.UITests — the new test passes; the 12 failures in that suite are pre-existing in this container (ktsu.png is an unfetched Git LFS pointer, so GetOrLoadTexture throws) and are identical with and without this change.

Docs updated: ImGui.Widgets/README.md (feature entry plus a Property Grid section), the root README.md widget lists, and CLAUDE.md (widget list, key files, and a Property grid section covering the section suppression, the browse handshake, the resolver contract, the per-row button ids and the list probe names).

🤖 Generated with Claude Code

https://claude.ai/code/session_01GTgzo1j271VvvXUNyLi3sL

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
83.7% Coverage on New Code
0.0% Duplication on New Code

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